Humanized antibody disulfide bonds

Romiplostim (AMG 531) is a member of new class of therapeutics called "peptibodies," which are peptides with key biologic activities covalently linked to antibody fragments that serve to extend the peptide s half-life. Romiplostim contains two disulfide-bonded human Fc fragments, each covalently attached through a polyglycine sequence to a peptide... 

In an attempt to increase efficacy in therapy, the production of bivalent or multivalent species by linking subunits (non-covalently, covalently, or by disulfide bonds) has been proposed. For example, a bispecific single-chain antibody fragment has been investigated for malaria therapy. This is a combination of two scFv, one directed against the CD3 molecule on human T lymphocytes, and the other against an epitope of a surface protein of Plasmodium falciparum, the parasite which causes malaria [8]. 

The antibodies are similar in structure to other globulin proteins which are present in serum of vertebrates [9], The antibody molecule consists of two light polypeptide chains and two heavy polypeptide chains [10]. The amino acids are present in all the chains but the number of residues and the sequence will vary in different antibody multiforms [9], Light chains contain approximately 220 amino add residues and heavy chains about 450 residues. The complete sequence of the chains of human IgG myeloma protein has been determined by Edelman [11], The chains are held together in the unique conformational structure of the antibody molecule by a few covalent disulfide bonds between the chains and many electrostatic bonds between the amino groups of one chain and the hydroxyl groups of another chain. The covalent bonds are represented in Formula 1, 2 and 3 [peptide, disulfide and... 

Elhott S, Chang D, Delorme E, Dunn C, Egrie J, Giffin J, Lorenzini T, Talbot C, Hesterberg L. Isolation and characterization of conformation sensitive antieryth-ropoietin monoclonal antibodies effect of disulfide bonds and carbohydrate on recombinant human erythropoietin structure. Blood 1996 87 2714-22. 

An IgG molecule consists of two heavy chains and two light polypeptide chains connected through disulfide bonds (Figure 1). IgG antibodies have a molecular weight of 150 Kd and account for approximately 80 ( of the total immunoglobulin in human serum. 

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